Master cylinder for a motorcycle/bike or the like brake or clutch

ABSTRACT

A brake/clutch master cylinder for a motorcycle/bicycle or the like, with a body which is produced by moulding of plastics material reinforced by glass fibre without the need for machining operations or metal inserts and which forms, together with the cylindrical shell of the master cylinder, a hydraulic-fluid reservoir, a coupling sleeve for a male quick-fit hydraulic connector, and a seat for fixing to a handlebar, the body having a high degree of structural stiffness with respect to working stresses and adequate resilience for impact stresses imparted to the body by means of the hand operating lever.

FIELD OF THE INVENTION

[0001] The present invention relates to a brake or clutch mastercylinder to be mounted on the handlebars of a motorcycle, bicycle, orthe like.

BACKGROUND OF THE INVENTION

[0002] It is known that hydraulic braking systems are being used evermore widely in light vehicles such as motorcycles and bicycles.

[0003] For these vehicles, the control or master actuator has to satisfyvarious requirements including: low cost, light weight, resistance toatmospheric agents, impact strength and an ability to withstand highworking stresses, ease of installation on and removal from the vehicle,ease of connection to the braking system, as well as ease of replacementof the mechanical hand-operating element constituted by the hand leverwhich is most exposed to knocks and to the risk of breakage that doesnot prejudice the functionality of the other parts of the brakingsystem.

STATE OF THE ART

[0004] In order to satisfy at least some of these requirements, it hasbeen proposed, as described in U.S. Pat. No. 3,802,200, to produce thecontrol actuator (master cylinder) by the moulding of plastics material,with a small number of parts and machining operations, which are,however, necessary, and to associate a hydraulic-fluid reservoir withthe actuator.

[0005] A structure which is light, relatively inexpensive, and resistantto atmospheric agents is thus produced, but the other requirements arenot adequately satisfied.

[0006] In particular, the desirable strength of the cylinder and of thestructure with respect to working stresses and to knocks is notachieved. Moreover, any repairs are difficult because they involve therisk of loss of hydraulic fluid.

[0007] To achieve greater strength of the cylinder body, it has beenproposed, for motor vehicles, as described in the document EP 0185165,to make the body of plastics reinforced by a metal core, with clearconstructional complications and increased cost.

[0008] Alternatively, as described in U.S. Pat. No. 5,121,686, it hasbeen proposed to form the cylinder body in plastics reinforced withglass fibres, thus in practice excluding the possibility of subsequentmachining operations, to avoid which it is necessary to resort tocomplications in the moulding process and to constructional andproduction complications in order to produce the elements for connectionto the hydraulic circuit.

[0009] All of this is detrimental to cost and to ease of installation,setting-up, and repair, if necessary.

[0010] It should be added that these last two documents do not takeaccount of the particular characteristics of motorcycle brake or clutchoperating devices, which are hand operated and in which the device issubjected to risks of knocks and to working stresses quite differentfrom those which arise in vehicle master cylinders, which are subjectedsubstantially to purely axial stresses.

SUMMARY OF THE INVENTION

[0011] The disadvantages of the prior art are overcome and all of therequirements desirable for a motorcycle or bicycle brake are achieved bythe brake (or clutch) master cylinder of the present invention in whichthe cylinder body is produced by moulding of plastics materialreinforced with glass fibre, without constructional complications,without the need for machining operations, and without the need forauxiliary elements for connection to the hydraulic circuit, or for metalinserts.

[0012] Connection to the hydraulic circuit is achieved by a simple seatfor a male quick-fit connector restrained by a clip and the same clipsystem is used to render the hydraulic piston and its accessoriescaptive in its seat.

[0013] The cylinder body also incorporates a hydraulic-fluid reservoirthe walls of which strengthen the structure of the body and provide arigid frame for the anchorage of two support lugs of the articulationpin of the operating lever and for a seat for fixing to the handlebar ofthe vehicle.

[0014] A strong and compact structure which takes up little space, whichhas good stiffness and ability to withstand working stresses and which,at the same time, is relatively resilient and able to absorb stressesresulting from possible knocks is thus produced, in combination withconsiderable ease of installation, of setting-up of the hydraulicsystem, and of repair if necessary, and with an extremely low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The features and advantages of the invention will become clearerfrom the following description of a preferred embodiment, given withreference to the appended drawings, in which:

[0016]FIG. 1 is a perspective view of a cylinder unit formed inaccordance with the present invention and fitted on a vehicle handlebar,

[0017]FIG. 2 is an exploded view of the cylinder of FIG. 1,

[0018]FIG. 3 is a view of the cylinder of FIG. 1, in section, from above(with reference to the view of FIG. 1),

[0019]FIG. 3A is a detail view showing, in diametral section, acomponent of the cylinder of FIG. 1 for locating a primary seal and atthe same time completing a supply path for the hydraulic fluid,

[0020]FIG. 4 is a section, taken on the line C-C of FIG. 3, through aconstructional detail of the cylinder,

[0021]FIG. 5 is a section, taken on the line B-B of FIG. 3, through thebody of the cylinder of FIG. 1,

[0022]FIG. 6 is another section through the cylinder body, taken on theline D-D of FIG. 3,

[0023]FIG. 7 is a view of the cylinder body of FIG. 1 seen from theopposite side to the view of FIG. 3,

[0024]FIG. 8 is a schematic perspective view of the structure formed bythe cylinder body of FIG. 1, and

[0025]FIG. 9 is a second schematic view of the structure formed by thecylinder body of FIG. 1, improved in accordance with the preferredembodiment, to achieve greater torsional resilience.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

[0026]FIG. 1 is an overall perspective view of a preferred embodiment ofthe motorcycle brake or clutch master cylinder unit fitted on amotorcycle handlebar.

[0027] The unit comprises a body 1 having a pair of lugs, of which onlyone, indicated 2, is visible in the drawing, and between which anoperating lever or handle 3 is articulated, the body 1 also having afixing seat connected, by means of fixing screws 5, 6, 7, 8, (which haverespective nuts, or are even self-tapping screws), to a complementaryseat 4 in order to fix the unit to the handlebar 9.

[0028] The cylinder of the master cylinder unit (in which the piston andits sealing members are housed) is formed inside the body 1 and the body1 at the same time forms a hydraulic-fluid reservoir which is incommunication with the interior of the cylinder and is closed by aremovable lid 10 with a plug/window 11 for checking the hydraulic-fluidlevel and possibly topping it up.

[0029] The body also has a hydraulic outlet constituted by a cylindricalhousing which is in communication with the chamber of the cylinder andin which a male quick-fit connector 12, which is connected, directly orby means of a male screw, to a pipe 24 for connection to the brake orclutch actuator member, is engaged.

[0030] The unitary body 1 is produced by moulding of plastics materialreinforced with glass fibre, preferably polyamide or polystyrene resinwith 30% of glass fibre, and constitutes a generally rectangularparallelepipedal box structure which is rigid and able to withstand thepressures developed by the operation of the cylinder as well as thestresses which the lever/handle imparts, when it is operated, to thebody 1, by means of the articulation restraint 15 and the interactionbetween the lever and the piston.

[0031] These stresses, which act in the plane defined by the lever andthe handlebar, that is, in the plane perpendicular to the axis ofpivoting of the lever (the articulation axis), are discharged, throughthe body and its fixing seat, onto the handlebar 9 which transfersequivalent and opposite restraint reactions to the body.

[0032] These aspects will be discussed in greater depth below.

[0033] It is appropriate here to consider another aspect: in the eventof a fall, the lever 3 is particularly exposed to especially violentstresses transverse the above-defined plane which, as often occurs inbraking devices of the prior art, may cause breakage of the lever or,worse, of the lever support structure.

[0034] It is therefore advisable for the unit to have a predeterminedresilience with respect to these stresses so as to absorb theinstantaneous stresses developed by the impact, to damp them, and toregain its original, undeformed configuration.

[0035] This result is achieved by a series of measures.

[0036] 1) The lever 3, like the body 1, is also preferably made ofplastics material filled with glass fibre and therefore, although it isstrong and quite rigid, has greater resilience than the light casting orforging alloys commonly used for the production of the lever, which areeither very brittle and break easily or are very plastic and bend easilybeyond the yield point, undergoing permanent deformation.

[0037] 2) The resilient effect of the plastics material of which thelever is made is enhanced by an appropriate configuration of itscross-section which ensures good stiffness for normal operative stressesin the plane perpendicular to the axis of the lever, but less stiffnessfor stresses transverse this plane.

[0038] In particular, as shown in FIG. 1, in the vicinity of thearticulation restraint 15, the cross-section 13 of the lever isapproximately oval (and advantageously recessed and provided with ribson the face not visible in the drawing) with a greater moment of inertiarelative to the neutral axis parallel to the articulation axis and alesser moment of inertia relative to the neutral axis perpendicular tothe former neutral axis. In the region farthest from the articulationrestraint, however, the cross-section 14 of the lever is approximatelycircular (and possibly recessed on the side which is not visible) for amore comfortable grip.

[0039] 3) The support lugs of the articulation restraint 15 have goodresistance to tension/compression stresses in the plane perpendicular tothe articulation axis and discharge them through the side wall of thebody 1 onto the lower wall or base of the body and through the body tothe fixing seat and to the handlebar.

[0040] Conversely, stresses transverse the plane perpendicular to thearticulation axis bring about a resilient twisting of the side wall ofthe body 1 on which the lugs are positioned and a correspondingbending/twisting of the lower wall and of the other walls, with aneutral axis oriented in the direction in which the moment of inertia ofthe cross-section is lowest. These aspects will be explained furtherbelow.

[0041]FIG. 2 shows the cylinder unit of FIG. 1 in an exploded view, forgreater clarity.

[0042] A cylindrical shell 16 moulded in the body 1 is open at one endand forms the pressure chamber of the cylinder, with an inner portion,relative to the open end, having a diameter equal to that of a piston17, and an outer portion of larger diameter suitable for housing, inorder, a primary seal 18, a spacer 19, a secondary seal 20, and a guidesleeve 21 for the piston 17.

[0043] A compression spring 22 is fitted between the closed end of thechamber and the head of the piston 17.

[0044] The closed end of the chamber has an opening (not visible in thedrawing) communicating with the interior of a hydraulic coupling sleeve23 in which a male quick-fit hydraulic connector 12 is engaged and heldin its seat by a forked locking element 25 engaged by sliding insuitable holes moulded in the sleeve 23.

[0045] Similarly, once the piston 17 and its accessories have beenfitted in the pressure chamber, they are restrained in the chamber by aforked locking element 26 engaged by sliding in suitable holes mouldedin the shell 16. Only the rod 66 for operating the piston 17, which hasa smaller diameter than the piston, projects freely from the shell inorder to interfere with a thrust appendage 37 of the lever 3.

[0046] The body 1 as a whole constitutes a box structure configuredapproximately as a rectangular parallelepiped, containing more than halfof the shell 16 and forming a hydraulic-fluid reservoir with a base, notvisible, constituted partially by the shell 16, and side walls on one 27of which the lugs 2, 28 for the articulated restraint of the lever arepositioned, reinforced by suitable ribs.

[0047] A seat 29 for fixing to the handlebar, positioned on another wallof the reservoir and on the base, is moulded integrally with the body 1and has suitable recesses for reducing weight, and through-seats 30, 31,32, 33 for the fixing screws (5, 6, 7, 8 in FIG. 1).

[0048] The reservoir is closed by the lid 10 after the interposition ofa bellows-like pressure-compensation diaphragm 34 between the lid andthe side walls of the reservoir with a filling/topping-up opening 35connected to a corresponding opening of the reservoir and closed by aplug/window 11. The reservoir is in communication with the pressurechamber through one or more holes such as the hole 36 formed by a mouldpin. FIG. 3 shows the body 1 in section, with a view from above and incomposite section (a median section through the body 1 in the lowerportion and a diametral section through the cylindrical shell 16 of thepressure chamber, as indicated by the section line A-A of FIG. 5), withthe various components of the master cylinder housed in the shell 16 andidentified by the same reference numerals are used in FIG. 2.

[0049] It can be noted that the base 38 of the reservoir, the peripheralwalls 27, 39, 40, 41 of which can be compared to reinforcing ribs,constitutes, together with the shell 16, a rigid structure which isparticularly able to withstand stresses oriented in the plane of thedrawing, and on which the lugs such as 28 and the fixing seat 29 arepositioned.

[0050] It will also be noted that the side 39 of the reservoir is notstraight but is constituted by two portions which are slightly inclinedto one another (or alternatively is slightly curved) for the reasonswhich will be made clearer below.

[0051] With regard to the actuator member, it will be noted that it isof the type with a piston which is slidable on the seals, rather thanwith seals slidable with the piston in the cylinder.

[0052] This ensures a much longer useful life of the seals and improvedsealing since the piston can be moulded of non-filled plastics materialso as to ensure dimensional accuracy and better surface finishing thancan be achieved by the moulding of plastics material rein forced withglass fibre.

[0053] In order to operate correctly, the primary seal 18 which is ofthe type with two lips acting on the piston and on the cylindrical wallof the chamber, respectively, must be subjected to controlled or zeroaxial compression.

[0054] The pressure chamber therefore has an abutment step 48 for thespacer 19 for ensuring its correct axial positioning and controlling theaxial compression exerted on the seal.

[0055] Alternatively, instead of the step 48, the axial positioning ofthe primary seal 18 may simply be achieved by the positioning of theforked locking element 26 which takes up the dimensional tolerances ofthe spacer 19, of the secondary seal 20, and of the guide sleeve 17 inan axial direction so as to impose a controlled maximum compression onthe primary seal.

[0056] The spacer 19 has the dual functions of preventing axialmovements of the primary seal 18 (due to the pressure developed in thepressure chamber) and of establishing a connection between the pressurechamber and the supply hole (or holes) 36 when the piston is at rest.

[0057] For this purpose, as can be seen more clearly in FIG. 2 and inthe section of FIG. 3A, the spacer in the form of a cylindrical ringhas, on its outer cylindrical wall, an annular recess 49 and radialholes 50 for communication between the outer annular recess 49 and theinterior of the ring. The two end walls 51, 62 of the cylindrical ring,however, are flat and continuous. With this arrangement of the recess,the height of the step 48 in the pressure chamber, if a step isprovided, can be kept very small and sufficient to ensure the abutmentof the spacer 19 which, with its end surface 51, ensures continuoussupport for the primary seal 18 when the seal 18 is subjected topressure.

[0058] It is thus possible to ensure minimal radial dimensions of thespacer 19, the secondary seal. 20, and the sleeve 21, even in thepresence of the step 48, consequently also limiting the radial dimensionof the shell 16.

[0059] Clearly the spacer is positioned axially in the shell in a mannersuch that the annular recess 49 is located in the region of the supplyhole 36 and the piston 17 has, at its end, in known manner, longitudinalgrooves 52 which put the pressure chamber into communication with theinterior of the spacer ring when the piston is at rest.

[0060]FIG. 4 shows, in a section taken on the line C-C of FIG. 3, theconstructional detail of the body 1 constituted by the sleeve 23 forhydraulic coupling with a male quick-fit hydraulic connector.

[0061] Two parallel holes 42, 43 extend through the sleeve 23 forreceiving the forked locking element 25 which is advantageously shapedfor engagement in a locking groove of the male hydraulic connector 12.

[0062]FIG. 5 shows the body 1 in a section taken on the line B-B of FIG.3 and shows its structure which encloses both the reservoir and thepressure chamber in a compact space.

[0063] It also shows clearly that the wall 41 of the reservoir which isprovided with a pair of brackets or appendages 44, 45 that areadvantageously recessed to ensure a uniform combined thickness withconsiderable stiffness, itself at least partially constitutes the seat29 for fixing to the handlebar, so that the stresses exerted by thelever 3 on the body 1 by means of the lugs are discharged directly ontothe fixing seat.

[0064] The further advantage of a saving in material (to which theincorporation of the shell 16 in the reservoir as a partial constituentof the base 38 of the reservoir contributes), and of the consequentreduction in weight of the unit, is thus also achieved.

[0065]FIG. 6 shows the body 1 in a section taken on the line D-D of FIG.3, basically to make clear two aspects.

[0066] 1^(st)) The open end of the cylindrical shell 16 projects outsidethe reservoir wall 27 and two parallel holes 46, 47 extend through itfor receiving the forked locking element 26 which is advantageously madeof glass-fibre-reinforced plastics, and which prevents the sleeve 21 andthe piston 17 from slipping out of the shell 16.

[0067] The distance between the prongs of the forked element 26 isnevertheless sufficient to allow the actuation rod 66 to pass freely.

[0068] Even if the lever 3 is removed in order to be replaced in theevent of breakage, the sleeve and the piston are thus prevented fromslipping out of the shell 16, with a consequent leakage of hydraulicfluid, when the retaining effect is no longer exerted by the appendage37.

[0069] 2^(nd)) The lugs 2, 28, disposed on either side of the plane ofthe base 38, are connected to the fixing seat 29 by two continuous ribs53, 54 which include the portion of the shell 16 that projects from thereservoir wall 27.

[0070] The lugs 2, 28 are positioned, respectively, on the wall 27 andon a suitable extension 55 thereof, visible more clearly in FIG. 7.

[0071] Reinforcing ribs 56, 57 stiffen the connection between the lug 2and the wall 27 and between the extension 55 and the base wall 38,respectively.

[0072] A structure is thus produced which is particularly capable ofwithstanding stresses acting in the plane perpendicular to thearticulation axis, which are discharged through the ribs and the base 38of the reservoir onto the support seat, with minimal deformation.

[0073] The situation which arises when the structure is subjected to atwisting or bending stress due, for example, to a force resulting froman impact, applied to the lever and oriented in a plane extendingthrough the articulation axis, is completely different.

[0074] This situation is shown schematically in the axonometric view ofFIG. 8.

[0075] If a bending moment, represented by the arrow M, is applied tothe lugs 2, 28 through the articulation restraint, the lugs tend to bendand, by means of the ribs, apply a twist to all of the walls of thereservoir but particularly to the side 27 on which the lugs arepositioned and to the base 38, which tend to be disposed in the positionindicated in broken outline.

[0076] Clearly, the moment of inertia of the box structure and inparticular of the cross-section of the side 27 and of the cross-sectionof the base 38 is minimal for stress in this direction.

[0077] However, the other walls also contribute to the stiffness of thesystem.

[0078] This contribution (as shown schematically in FIG. 9) canpreferably be minimized by disconnecting the other walls, for thepurposes of the twisting stress, which involves a degree of compressionof the straight wall 39 between the wall 27 stressed by the lug 2 andthe wall 40 which tends to offer resistance.

[0079] In other words, the wall 39 can be compared to some extent to arod loaded at a point.

[0080] However, as already stated, the wall 39 is preferably curved (oris even composed of two portions inclined to one another) so that, evenin the presence of a compression force below the critical load, it tendsto bend, rendering the reaction of the wall 40 to the deformation of thewall 27 minimal. The structure can therefore resiliently absorbtorsional stresses resulting from an impact.

[0081] The foregoing description relates purely to a preferredembodiment and it is clear that many variations may be adopted withoutdeparting from the scope of the invention.

[0082] For example, the sleeve 17 (FIG. 3) may have, at its end whichbears on the forked element 26, a constriction which, independently ofthe forked element 26, prevents the piston 17 from coming out of itsseat, without interference with the rod 66.

[0083] Moreover, instead of forming a cylindrical seat of uniformdiameter as shown in FIG. 3, the sleeve 23 may form an inner cylindricalseat of smaller diameter for housing the end of a male hydraulicconnector and a respective seal with a minimal diameter.

[0084] This is in order to reduce to the minimum the axial stressdeveloped by the pressure when the brake is operated.

[0085] The outer part of the cylindrical seat, on the other hand, mayhave a larger diameter to ensure the necessary mechanical strength andmanipulability of the axial locking system.

What is claimed is:
 1. A brake or clutch master cylinder for amotorcycle/bicycle or the like, of the type in which a body mounted on ahandlebar forms a): a cylindrical shell for holding hydraulic fluid,closed by a piston which is operated by a hand lever in order totransfer the hydraulic fluid held in the shell to an actuator device,and b): the walls of a hydraulic-fluid reservoir communicating with theinterior of the shell, wherein: the body is produced by moulding ofplastics material reinforced with glass fibre, with the exclusion of anymachining operations or metal inserts, the body has a sleeve forming ahousing communicating with the interior of the cylindrical shell for theinsertion of a male quick-fit hydraulic connector, locked axially by afirst forked locking element inserted in at least one through-hole inthe sleeve, the piston being held captive in the shell by a secondforked locking element inserted in through-holes in the shell, the shellis partially contained in the volume of the reservoir with the axis ofthe cylindrical shell extending through the volume of the reservoir, andthe walls of the reservoir form a support structure for two lugs onwhich the hand lever is articulated, and for a seat for the fixing ofthe body to a handlebar.
 2. A master cylinder according to claim 1 inwhich the body has a sleeve forming a housing, communicating with theinterior of the cylindrical shell, for the insertion of a male quick-fithydraulic connector, locked axially by a second forked locking elementinserted in at least one through-hole in the sleeve.
 3. A mastercylinder according to claim 1 or claim 2 in which the hand lever is madeof plastics reinforced with glass fibre and the cross-section of thelever in the vicinity of the articulation lugs has a greater moment ofinertia for stresses acting in the plane perpendicular to thearticulation axis than it has for stresses transverse that plane.
 4. Amaster cylinder according to claim 1 in which the walls of the reservoirform a support structure for the lugs which has a greater stiffness withrespect to stresses acting in the plane perpendicular to thearticulation axis than it has with respect to stresses transverse thatplane.
 5. A master cylinder according to claim 4 in which the walls ofthe reservoir comprise a base, and a first side wall and a second sidewall which are adjacent, flat and perpendicular to one another and tothe base, as well as a third side wall and a fourth side wall which areperpendicular to the base and opposite the first and second walls,respectively, and in which: the first side wall constitutes part of thefixing seat, and the lugs are positioned on the second side wall and onan extension of the second wall, on one side and on the other side ofthe plane of the base, respectively.
 6. A master cylinder according toclaim 5 in which the third wall is formed by at least two portions whichare perpendicular to the base and are inclined to one another.
 7. Amaster cylinder according to claim 1 in which a primary seat housed inthe shell is held in position in the shell axially by a spacer elementin the form of a cylindrical ring with flat and continuous ends, thecylindrical ring having an annular recess in its outer wall and radialholes for putting the annular recess into communication with theinterior of the cylindrical ring.